Stirling Heat Engine:
The Stirling engine, invented by Robert Stirling in 1816, can be more efficient than a gasoline or a diesel engine and it is very much different than the internal combustion engine in your car. The engine uses the Stirling cycle, which uses gas as working substance. The fixed amount of gas is transferred back and forth between cold and hot ends of a cylinder. The hot end is heated
by an external heat such as fire while the other side is cooled with ice. The gas chambers of each cylinder are connected and there are pistons also connected to each other. The pistons are connected mechanically by a linkage that will determine how they will move.
First, heat is added to the gas on the heated end causing pressure to build up and forces the piston to move down. The left piston moves up while the right on is down. The gas is pushed from the heated end to the cooled end, lowering the pressure. The piston on the cool end starts to compress the gas and heat is generated by this. The right piston moves up while the left piston moves down and this causes the gas to be pushed into the heated end, repeating the cycle.
Other types of Stirling engines are:
-Displacer-type Stirling Engine (a displacer controls when the gas chamber is heated or cooled)
-Two-Piston Stirling Engine (The heated cylinder is heated by an external flame. A rod comes out of each piston and is connected to a small disc, which is connected to a large flywheel.)
Most Stirling engines are invisible to us today, however they are used in machines such as submarines, cryocoolers, auxiliary power generators in yachts, and there are stirling engines used in classrooms as well.
Peltier Device:
A Peltier thermo-element is a device that uses the Peltier effect to activate a heat pump. The Peltier is made of semi
conductive material so it as many positive-negative contacts connected in the series. It has two plates, a cold and a hot plate, and in between there are several thermo couples. The thermo couples are connected together with two wires sticking out of it. Voltage is applied to the wires and the heat is transferred from one plate to another.
This device is also called a Peltier heat pump, solid state refrigerator, or thermoelectric cooler. It can be used for cooling or for heating, although it is more commonly used for cooling. It is used in drink coolers and computers use this to keep the device cool. Even though, not many computers use it now, if you have an old computer it is likely to use it.
References:
http://auto.howstuffworks.com/stirling-engine.htm
http://www.stirlingengine.com/faq/#5
http://pcbheaven.com/wikipages/The_Peltier_Thermo-Element/
http://www.survival-manual.com/electricity/peltier-elements.php